PROJECT SUMMARY Infertility and pregnancy loss are common health disorders affecting women. Uterine glands have important biological roles in fertility, dysplasia and disease. Pregnancy loss is the most common complication of human gestation, and recurrent pregnancy loss and infertility are observed in uterine gland knockout animal models. Uterine glandular epithelia (GE) and, by inference, their secretions have biological roles in uterine receptivity, blastocyst/conceptus survival and implantation, and stromal cell decidualization- all essential processes for the establishment and maintenance of pregnancy. However, uterine gland biology research is hampered by the lack of suitable mouse models to conditionally delete or overexpress genes specifically in the GE of the adult uterus. The goal of this proposal is to address that problem. Prss29 (protease, serine 29 or implantation serine proteinase gene two) is a gene expressed robustly and specifically after puberty in the GE of the adult mouse uterus and not in other female reproductive tract tissues. In Aim 1, improved Cre recombinase (iCre) will be inserted into the 3? untranslated region of the Prss29 gene using CRISPR/Cas9 genome engineering. Activity and cell-specific expression of iCre will be determined in the developing and adult tissues using Rosa26 reporter mice. Aim 2 is to establish and validate the usefulness of Prss29- iCre mice for study of adult uterine gland function. Forkhead box a2 (Foxa2) is specifically expressed in the GE of the adult mouse and human uterus and has a potential biological role in regulation of ovarian steroid hormone responsive genes and GE function during pregnancy. Prss29-iCre mice will be used to conditionally delete Foxa2 in the adult uterus and determine its impact on fertility and pregnancy. Prss29-iCre mice will be used in conjuction with RiboTag mice to isolate actively translated mRNAs, which will be sequenced to uncover the GE active transcriptome of pregnancy. This application specifically targets NIH program announcement PA-13-303 entitled ?NIH Exploratory/Developmental Research Grant Program (Parent R21)? that encourages research grant applications to support the early and conceptual stages of a project. At the conclusion of these studies, we expect to have generated a novel mouse model useful for the study of uterine gland biology, regeneration, and disease and fill a significant gap in our existing knowledge of uterine gland function during pregnancy.